Aspects of the present disclosure generally relate to seed treatment formulations, treated (e.g. coated) seeds, and methods of protecting emerging root systems from fungal growth. In particular, embodiments of the seed treatments described herein are capable of reducing and/or substantially eliminating fungal contaminants from emerging root systems and the surrounding environment, where such fungal contaminants include but are not limited to species of Fusarium, Pythium, and Rhizoctonia. 
The increasing popularity of spinach among consumers has caused a significant increase in the amount of spinach grown in the U.S. in recent years. Persistent pathogenic infection of spinach and other leafy greens in the early stages of development, however, can cause up to a 70% loss in yield (see Larsson et al., “Disease progression and yield losses from root diseases caused by soilborne pathogens of spinach,” Phytopathology 82:403-406 (1992)), resulting in substantial economic loss for growers and increased food prices for consumers. Specifically, spinach and leafy greens are particularly susceptible to infection by “damping off” complexes and similar root rot diseases, which can cause poor germination and root establishment in infected fields during the first week of development. In infected soils, for example, yield may decrease as the result of desiccation or death of seedlings either pre- or post-emergence, as well as poor overall growth and yellowing of leaves. Susceptibility to such “damping off” and root rot can be exacerbated by poor field conditions, including overwatering, inadequate drainage, and/or crowded planting. While various pathogenic species found in soil can cause “damping off” or root rot, the more common pathogens include fungal species and fungi-like species (oomycetes) of Fusarium, Pythium, and Rhizoctonia. The poor emergence and/or growth of seedlings due to “damping off” and/or root rot may also affect other crops, including corn, wheat, potato, and soybean, among others.
In general, control of damping off and root rot has been attempted by a variety of methods. One method that may be employed in an effort to reduce or eliminate damping off is to sow seeds in a sterilized growing medium; however, such a method may prove ineffective as fungal spores may be introduced to the growth medium either on the seeds themselves or after sowing (e.g. in water or by wind). Methods requiring sterile growing environments may also be impractical and/or increase costs, particularly for commercial growers managing significant crop acreage. Further methods to prevent damping off include soil drenches, which are not economical due to the fast production cycle where time from planting to harvest is less than 30 days. And, most soil drenches have the added undesirable requirement of long re-entry intervals before workers are permitted to return to the fields.
Another method widely used in the agricultural industry to control fungal infections is the use of fungicides. Fungicides such as metalaxyl (N-(methoxyacetyl)-N-(2,6-xylyl)-DL-alaninate), thiram (dimethylcarbamothioylsulfanyl N,N-dimethylcarbamodithioate), and ipconazole (2-[4(chloropheyl)methyl]-5-(1-methylethyl)-1-(1H-1,2,4-trazol-1-ylmethyl)cyclopentanol) have been shown to effectively control fungal infections in emerging root systems, but such use of conventional applied chemistries render these materials unsuitable for the commercial production of organic crops. Copper (II) hydroxide has also found widespread application in the agricultural industry as a fungicide and bactericide. Commercially available in liquid and water dispersible granule form (Champ®, Kocide®), copper (II) hydroxide formulations have, however, traditionally been applied to crop fields by spraying or otherwise coating the leaf surface (i.e. foliar sprays); that is, application occurs post-emergence. Such a contact fungicide in its typical spray form is thus ineffective to treat or prevent soil-borne fungal conditions that invade the emerging root system at the early stages of development (e.g. in the first week after planting).
Current seed treatments marketed for the prevention of damping off and root rot are available, but suffer from significant drawbacks. For the organic market in particular, such seed treatment formulations comprise microbial species, known as bio-pesticides, which are intended to mitigate the effects of insects or disease. Bio-pesticides can be difficult to control under constantly changing environmental conditions, including variations in soil and air temperature, humidity, soil moisture, and nutrient content. The slow growth of these microbial species is similarly problematic, as the microbes may not develop in a manner appropriate to outcompete soil pathogens for root colonization. This slow microbial growth is particularly disadvantageous with respect to Pythium and other fungal species, which become established in the emerging root system within just 7 to 10 days after planting.
To address the shortcomings of the methods currently available in the agricultural industry to mitigate or prevent damping off and root rot, it would be advantageous to provide a chemical seed treatment formulation that combines root development nutrition and root protection to combat both pre-emergence and post-emergence fungal infection, where the seed treatment is suitable for use in organic crop production.